Injection molding apparatus

ABSTRACT

An apparatus provided is capable of performing injection molding of a high-melting point metal. The injection molding apparatus comprises a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, and a raw material lump supplying means for supplying the raw material lump to the above-mentioned raw material accommodating part from above. For the purpose of ensuring that a melt of a metal which has been heated and melted hardly flows into a gap between the plunger and the sleeve, the above-mentioned plunger and/or sleeve is equipped with a cooling means.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of Application PCT/JP2005/000377, filed Jan. 14, 2005, which was published under PCT Article 21(2).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an injection molding apparatus, and more particularly to an apparatus which is suitable for the vacuum injection molding of a high-melting point metal, particularly an active metal such as an amorphous alloy, and capable of carrying out the high-speed injection molding of a melt of the active metal while maintaining a clean state thereof.

2. Description of the Prior Art

Recently, as an injection molding method capable of casting a molded article having no void with an active metal, a molding method which uses a sleeve movable toward a mold and is carried out by supplying a raw material lump into a raw material accommodating part formed by an inside wall of a sleeve and the upper end face of a plunger slidably disposed therein, heating and melting the active metal under vacuum, and injecting and filling it in a cavity of the mold has been proposed (see Japanese Patent No. 2977374, JP 10-296424 A, and JP 2001-246451 A).

In a usual die-casting machine using an injection temperature of about 800° C. (the type using a large amount of molten metal and equipped with a melting bath for supplying the molten metal), cooling of a plunger or a sleeve portion is performed (see JP 43-28806 B). In the above-mentioned vacuum injection molding machine which effects the injection at a higher temperature of about 1200° C. or more, however, cooling of a plunger or a sleeve is not performed as disclosed in the patent literatures mentioned above. Moreover, a piston ring is not used for a head portion of the plunger.

The reason why cooling is not performed in the vacuum injection molding machine is considered as follows. That is, since it is die casting of a cold chamber system and employs the system which melts a raw material lump by batch processing in the raw material accommodating part of the upper part of the sleeve, the material to be used is small and, therefore, it is necessary to not lower the temperature of the melting metal.

However, since in the conventional vacuum injection molding machine cooling of the plunger or sleeve is not performed, there is a high possibility that molten metal will flow into a small gap between the inner surface of the sleeve and the side of the plunger (piston) during injection and solidify therein. Consequently, the frictional resistance increases, and at the worst the plunger will become the immovable state within the sleeve and cannot effect injection.

When ceramic is used for the sleeve which requires heat resistance, there is a possibility that the sleeve itself may be destroyed due to the resistance of the solidified metal when the plunger is operated and the molten metal may spout out of the sleeve into a vacuum chamber.

Further, it has been thought that if the sleeve and the plunger of the above-mentioned vacuum injection molding machine are provided with a cooling mechanism, the temperature of the molten metal will not be increased and the injection can not be performed. Therefore, the conventional vacuum injection molding machine has been caught in such a dilemma that the plunger and the sleeve are not cooled and, as a result, the problems described above are apt to be produced conversely.

SUMMARY OF THE INVENTION

The present invention has been made in view of the prior art described above and its fundamental object is to provide an apparatus capable of producing a high-quality molded article, in which a melt of a metal which has been heated and melted hardly flows into a gap between a plunger and a sleeve, the sliding movement of the plunger can be smoothly performed in the sleeve, and consequently the injection can be performed stably, even in the injection molding of a high-melting point metal having a melting point of about 1200° C. or more.

A further object of the present invention is to provide an apparatus which, even in the case of an active metal such as an amorphous alloy, can perform injection molding of the active metal continuously with one raw material loading, without releasing the vacuum state in the space of a heating-melting section, and can carry out mass production of the injection-molded article of high quality at a low cost.

To accomplish the objects mentioned above, in accordance with a fundamental aspect of the present invention, there is provided an injection molding apparatus comprising a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, and a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, characterized in that the plunger and/or the sleeve mentioned above is equipped with a cooling means.

In accordance with an embodiment which can perform the injection molding continuously by one raw material loading, there is provided an injection molding apparatus comprising a mold, a sleeve disposed beneath the mold so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, and a raw material lump supplying means for supplying the raw material lump to the above-mentioned raw material accommodating part from above, characterized in that the plunger and/or the sleeve mentioned above is provided with a cooling means. Preferably, the raw material lump supplying means mentioned above comprises an accommodating device containing a plurality of raw material lumps, a means for transferring the raw material lump disposed in the accommodating device to an upper position above the device, and a means for transferring the raw material lump transferred onto the upper position of the accommodating device to a position above the sleeve.

In accordance with a preferred embodiment, the above-mentioned plunger has an internal space formed therein and extending along its axial direction and a cooling medium supply pipe disposed in the internal space so as to leave a space portion around its circumference, i.e. its leading end portion in the vicinity of a plunger head part and the circumference of a pipe wall, so that a cooling medium supplied through the above-mentioned cooling medium supply pipe may flow through the internal space of the above-mentioned plunger from its leading end. On the other hand, the above-mentioned sleeve is provided at its outer peripheral surface with a cooling jacket having a flow path formed in the shape of bellows in the circumferential wall. Preferably, the cooling jacket is divided.

In accordance with another preferred embodiment, different materials are used for the plunger and the sleeve. When the plunger and the sleeve are constituted so as to have different thermal expansion coefficients, it is effective in preventing formation of a gap therebetween. For example, the above-mentioned plunger is formed from a metal or alloy having a melting point of not less than 800° C., such as Fe, Ni, Co, Mo, W, Ta, and Nb, or part or all of the above-mentioned plunger is formed from ceramic. On the other hand, the above-mentioned sleeve is formed from ceramic.

Further, it is also effective to dispose a piston ring in the outer peripheral surface of the head part of the above-mentioned plunger or to form the above-mentioned plunger so as to have a main body part and a separate head part.

As described above, in the injection molding apparatus of the present invention comprising a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, and a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, since the plunger and/or sleeve mentioned above is equipped with a cooling means, a melt of a metal which has been heated and melted hardly flows into a gap between the plunger and the sleeve. Particularly, when the plunger has an internal space formed therein and extending along its axial direction and a cooling medium supply pipe disposed in the internal space so as to leave a space portion around its circumference, i.e. its leading end portion in the vicinity of a plunger head part and the circumference of the pipe wall, so that a cooling medium supplied through the above-mentioned cooling medium supply pipe may flow through the internal space of the above-mentioned plunger from its leading end, the fluid as the cooling medium is supplied in the state suffering little influence by heating in the upper part, and the upper part of the plunger can be cooled efficiently. Further, by using different materials for the plunger and the sleeve so that they have different thermal expansion coefficients, it is possible to effectively prevent formation of a gap therebetween. Consequently, since the sliding movement of the plunger in the sleeve may be smooth, injection can be done without any problem in sliding movement of the plunger, and it is possible to produce a high-quality casting article stably.

Further, by combining the injection mechanism with the raw material lump supplying means mentioned above, even in the case of an active metal such as an amorphous alloy, it is possible to perform injection molding of the active metal continuously with one raw material loading, without releasing the vacuum state in the space of the heating-melting section, and to carry out mass production of the injection-molded article of high quality at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages of the invention will become apparent from the following description taken together with the drawings, in which:

FIG. 1 is a fragmentary sectional front view schematically illustrating one embodiment of the vacuum injection molding apparatus of the present invention;

FIG. 2 is a sectional view schematically illustrating one embodiment of a plunger to be used in the vacuum injection molding apparatus of the present invention;

FIG. 3 is a fragmentary sectional side view schematically illustrating one embodiment of a sleeve and a cooling jacket to be used in the vacuum injection molding apparatus of the present invention;

FIG. 4 is a plan view of the sleeve and the cooling jacket shown in FIG. 3;

FIG. 5 is a sectional view of the sleeve and the cooling jacket shown in FIG. 3 taken along the line V-V;

FIG. 6 is a fragmentary perspective view illustrating a raw material lump supply mechanism to be used in the vacuum injection molding apparatus of the present invention;

FIG. 7 is a fragmentary sectional side view illustrating the raw material lump supply mechanism shown in FIG. 6;

FIG. 8 is a fragmentary plan view illustrating the raw material lump supply mechanism shown in FIG. 6;

FIG. 9 is a fragmentary sectional front view schematically illustrating one embodiment of the vacuum injection molding apparatus of the present invention, depicting the discharge process of a molded article; and

FIG. 10 is a fragmentary sectional view schematically illustrating another embodiment of the plunger to be used in the vacuum injection molding apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The characteristic feature of the injection molding apparatus of the present invention resides in that, as described above, in the injection molding apparatus comprising a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, and a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, the plunger and/or the sleeve mentioned above is equipped with a cooling means and thus a melt of a metal which has been heated and melted hardly flows into a gap between the plunger and the sleeve. That is, although the molten metal heated to a higher temperature becomes easy to flow into the gap between the plunger and the sleeve, the apparatus is characterized by the fact that it is possible to prevent this phenomenon and make the sliding movement of the plunger in the sleeve becomes smooth.

The present inventors, after pursuing a diligent study, have found that when the upper part of the plunger is cooled as mentioned above and the melt of the heated and molten metal is rapidly cooled and solidified in the state where it has slightly flowed into the gap between the plunger and the sleeve, it is possible to prevent further inflow of the molten metal into the gap and also prevent excess cooling of the molten metal. As a result, it is possible to perform the heating and melting of the metal lump without exerting so much influence thereon, an increase in the sliding resistance is slight because the portion which has flowed into the gap between the plunger and the sleeve and has been solidified is slight, and therefore there is no trouble in sliding movement of the plunger in the sleeve. The present invention has been perfected based on these findings.

For the purpose of cooling the upper part of the plunger efficiently, it is effective to form in the plunger an internal space extending along its axial direction and to dispose a cooling medium supply pipe in this internal space so as to leave a space portion around its circumference, i.e. its leading end portion in the vicinity of a plunger head part and the circumference of the pipe wall, so that a cooling medium supplied through the above-mentioned cooling medium supply pipe may flow through the internal space of the above-mentioned plunger from its leading end along the circumferential wall. By forming such a structure, the fluid as the cooling medium is supplied in the state suffering little influence by heating in the upper part, and the upper part of the plunger can be cooled efficiently. Further, for the purpose of cooling the upper part of the plunger efficiently, it is effective to dispose on the outer peripheral surface of the sleeve a cooling jacket having a bellows-like flow path formed in its circumferential wall, preferably a split cooling jacket so that the attachment thereof may be easily carried out, in combination with the cooling of the plunger. Further, the use of different materials for the plunger and the sleeve so as to have different thermal expansion coefficients is effective in preventing formation of a gap therebetween and decreasing the molten metal portion flowing into the gap between the plunger and the sleeve. The use of the different kinds of materials is also effective in decreasing the heat dispersion and in suppressing the rise in temperature of the plunger.

In accordance with a preferred embodiment of the injection molding apparatus of the present invention, it is provided, in combination with the above-mentioned injection mechanism, with a raw material lump supplying means for supplying a raw material lump to a raw material accommodating part formed by the inside wall of the sleeve mentioned above and the plunger from above. Consequently, it is possible to perform efficient raw material lump supply in a short time and to minimize the stroke of the plunger to prevent the defect of operation produced by the gap between the plunger and the sleeve. Further, the raw material lump heated by a heating source may be efficiently supplied to a cavity of the mold. Preferably, the raw material lump supplying means mentioned above comprises an accommodating device containing a plurality of raw material lumps, a means for transferring the raw material lump disposed in the accommodating device to an upper position above the device, and a means for transferring the raw material lump transferred onto the upper position of the accommodating device to a position above the sleeve. By such an arrangement, it is possible to make the apparatus compact and to perform efficient transfer and supply of the raw material lumps.

As being clear from the foregoing description, although the injection molding apparatus of the present invention may be applied to the whole field of injection molding of not only an active metal, such as an amorphous alloy, but also a high-melting point metal having a melting point of about 1200° C. or more, it can be particularly advantageously applied to the injection molding of an active metal, such as an amorphous alloy, which requires a vacuum chamber. Particularly, by combining the injection mechanism with the raw material lump supplying means mentioned above, a plurality of raw material lumps can be supplied to the raw material accommodating part of the upper part of the sleeve continuously and automatically, without releasing the vacuum state in a vacuum chamber. Consequently, even if the active metal which tends to be oxidized and to be deteriorated by overheating is used, it is possible to perform the injection molding continuously and automatically under vacuum. As a result, it becomes possible to carry out mass production of the high-quality injection molded articles at a low cost.

Now, the preferred embodiments of the present invention will be described below with reference to the attached drawings to describe other characteristic features as well as the functions and effects of the present invention.

FIG. 1 through FIG. 9 illustrate one embodiment of a vacuum injection molding apparatus of the present invention. In the figures reference numeral 1 denotes a mold which is composed of a fixed lower mold 2 and a movable upper mold 3. The lower mold 2 having a pouring gate 4 is fixedly secured to a main platen 7 which has a circular opening 6 in the corresponding position and they are sealed by a sealing member (not shown), such as an O-ring, disposed between them. A plurality of tie bars 9 are upstanding in parallel from the main platen 7, and to the upper ends thereof a stationary platen 10 is fixedly secured. Although the number of tie bars 9 is four in this embodiment, it is naturally not restricted to this number, and there is a case of three or two, or a case of more than four. A movable platen 11 attached to these tie bars 9 is adapted to be moved up and down by clamping cylinders 12 mounted on the stationary platen 10. The movable upper mold 3 having cavities 5 formed in the parting surface with the fixed lower mold 2 is fixedly secured to the lower part of the movable platen 11 through the medium of a fixing member 13 and a connection member 14 (which may be integral with the fixing member 13). This movable upper mold 3 moves up and down along with ascent and descent of the movable platen 11. Incidentally, the movable platen 1 1 and the fixing member 13 have aligned mold exhaust vents 15 formed in the predetermined positions thereof, and the sealing between respective two members of the movable platen 11, the fixing member 13, the connection member 14, the movable upper mold 3, and the fixed lower mold 2 is done by the sealing members (not shown), respectively.

A plurality of ejector pins 16 (although the illustrated embodiment includes a pair, it may also be three or more according to the number of cavities) are inserted into the mold 1 so as to be protrusible into the respective cavities 5. A connection rod 17 of these ejector pins 16 is inserted through the movable platen 11 and the fixing member 13 and constituted so that the lower end face of each ejector pin 16 may be flush with the top faces of the mold cavities 5 by a means for urging it upward and a stopper means (not shown). Incidentally, if the movable platen 11 is elevated up to an upper dead point after completion of injection molding, the upper end face of the connection rod 17 comes into contact with the lower end face of a cylinder rod 19 of an ejector cylinder 18 attached to the stationary platen 10 so as to be aligned with the connection rod. When the ejector cylinder 18 is actuated, the cylinder rod 19 depresses the connection rod 17, and the ejector pins 16 protrude into the respective cavities 5.

Further, a cylindrical vacuum housing 20 suspending so as to surround the movable upper mold 3 is fixedly secured to the underside of the movable platen 11 through the medium of a sealing member (not shown). On the other hand, a sealing frame 21 is similarly fixedly secured to the top surface of the main platen 7 at the corresponding position through the medium of a sealing member (not shown). Accordingly, when the movable platen 11 descends to perform the clamping of the movable upper mold 3 to the fixed lower mold 2, the outer surface of the vacuum housing 20 slides on the inner surface of the sealing frame 21 through the medium of a sealing member (not shown) to form a sealed injection molding section space X.

Further, a molded article discharge cylinder 22 equipped with an arm part 23 which is capable of approximating to and retreating from the injection molding section at a predetermined height is attached to the main platen 7 in a predetermined position (shown only in FIG. 9 for convenience sake of illustration).

On the other hand, a vacuum chamber 24 for forming a heating-melting section space Y in a sealed manner is arranged underneath the main platen 7 and supported by a frame (not shown). The shut-off and the communication between the injection molding section space X mentioned above and the heating-melting section space Y in the vacuum chamber 24 are performed through the closing and opening of the opening 6 by a shielding shutter 26 which is actuated by a shutter cylinder 25 (shown only in FIG. 9 for convenience sake of illustration) so as to slide forward and backward while being in contact with the underside of the main platen 7. Incidentally, the shielding shutter may be the pivot type.

One line L1 (mold exhaust line) of the vacuum evacuation system of a vacuum pump (comprised of a diffusion pump and a rotary pump) is connected to the mold exhaust vents 15 formed in the movable platen 11 and the fixing member 13 to evacuate the injection molding section space X until it reaches a predetermined degree of vacuum. Another line L2 is connected to the vacuum chamber 24 to evacuate the heating-melting section space Y until it reaches a predetermined degree of vacuum. Further, a mold air valve for releasing the vacuum state of the injection molding section space X and a vacuum reserve tank (not shown) are also connected to the mold exhaust line L1 so that the vacuum state may be formed in the injection molding section space X instantaneously after the clamping of the movable upper mold 3 to the fixed lower mold 2.

Further, an inert gas container may be also connected to the vacuum chamber 24 so that the heating and melting can be carried out under an inert gas atmosphere, such as argon, depending on a raw material to be used.

A cooling jacket of the two-part split type is disposed in the vacuum chamber 24 in a position underneath the pouring gate 4 of the fixed lower mold 2 and the opening 6 of the main platen 7 in alignment with these parts and attached to a cylindrical sleeve 27 so as to surround it. The sleeve 27 and the lower end part of the cooling jacket 28 are fixedly secured to a vertically reciprocating plate 31 through the medium of a holding member 30. This vertically reciprocating plate 31 is actuated by a sleeve moving cylinder 32 to vertically reciprocate the sleeve 27 and the cooling jacket 28 as a whole while being guided with a guide bar 36. Accordingly, when the sleeve moving cylinder 32 is actuated and the vertically reciprocating plate 31 is vertically reciprocated, the sleeve 27 and the cooling jacket 28 elevate toward the pouring gate 4 of the mold 1 and descend to the original position.

On the other hand, the sleeve 27 and the cooling jacket 28 are equipped with a plunger 33 slidably disposed therein. This plunger 33 is actuated by an injection cylinder 35 attached thereto through the medium of a vertically reciprocating plate 34 and adapted to vertically slide in the sleeve 27 and the cooling jacket 28 while being guided with the guide bar 36.

A high-frequency induction heating coil 37 as a heating means is arranged in the perimeter of the upper part of the sleeve 27. As a heating means, it is not restricted to the high-frequency induction heating, and it is natural that any other well-known heating methods, such as resistance heating, may be adopted.

As shown in FIG. 2, the above-mentioned plunger 33 comprises a cap-like head part 38, a hollow body part 39 screwed into this head part 38, a hollow pipe part 40 fixedly secured to the lower end part of this body part 39, an upper base part 41 to which the hollow pipe part 40 is attached, a lower base part 42 fixedly secured to this upper base part 41, and a cooling medium supply pipe 43 of which lower end is attached to the upper base part 41 so as to extend in the axial direction in the internal spaces of the above-mentioned head part 38, the hollow body part 39, and the hollow pipe part 40. The cooling medium supply pipe 43 is arranged so that it may leave a space portion around its circumference, i.e. its leading end portion in the vicinity of the plunger head part and the circumference of the pipe wall, the above-mentioned space portion communicates with a flow path 44 formed in the upper base part 41, and the lower end of the cooling medium supply pipe 43 communicates with a flow path 45 formed in the lower base part 42. Accordingly, a cooling medium, such as water and oil, supplied through the cooling medium supply pipe from the flow path 45 formed in the above-mentioned lower base part 42 flows through the internal space of the plunger mentioned above from the leading end of the cooling medium supply pipe 43 along the circumferential wall and is discharged from the flow path 44 formed in the upper base part 41. Further, two piston rings (which may be an arbitrary number) 46 are attached to the outer peripheral surface of the upper part of the above-mentioned head part 38 so that their surfaces may be flush with this outer peripheral surface. In such structure, the fluid as the cooling medium is supplied in the state suffering little influence by heating in the upper part, and the upper part of the plunger can be cooled efficiently. For example, when the metal lump placed in the top end face of the plunger is heated and melted at about 1200° C., the temperature of the upper end portion of the above-mentioned head part 38 will become about 800-900° C. and that of the part of the cooling medium supply pipe 43 near the leading end will become about 500-600° C. Incidentally, as a material of the head part 38 which is exposed to a high temperature, ceramics are preferred.

On the other hand, as described above, the cooling jacket 28 of the two-part split type is attached to the circumference of the sleeve 27 so as to surround it, as shown in FIG. 3 through FIG. 5. The cooling medium flow paths 29 a and 29 b in the shape of bellows are formed in the side walls of respective jacket portions 28 a and 28 b independently, and the cooling medium pipes 29 are attached to these cooling medium flow paths 29 a and 29 b, respectively (see also FIG. 6).

In the vacuum chamber 24, a raw material lump supplying apparatus 47 is arranged in the neighborhood of the above-mentioned sleeve 27. This raw material lump supplying apparatus 47 comprises a turntable 48, a plurality (although in the illustrated embodiment it is four, two or three or more than five may be adopted) of raw material accommodating cylindrical bodies 49 of the shape of upright cylinder installed on the turntable in such a positional relation that its upper end is aligned with the height position of the above-mentioned sleeve 27, a vertically reciprocating pin 51 which functions as a means for transferring the raw material lump A placed in the raw material accommodating cylindrical body 49 upward, and an arm 50 which functions as a means for transferring the raw material lump A transferred onto an upper position above the raw material accommodating cylindrical body 49 to a position above the sleeve, as shown in FIG. 6 through FIG. 8. Incidentally, the turntable 48 and the raw material accommodating cylindrical bodies 49 installed thereon constitute a cassette accommodating device, and after all of the raw material lumps placed in respective raw material accommodating cylindrical bodies 49 has been used, it is replaced with a new cassette accommodating device as a whole.

The turntable 48 has hole portions 53 formed in the positions where the raw material accommodating cylindrical bodies 49 are installed. The vertically reciprocating pin 51 inserted in this hole portion 53 transfers stepwise the raw material lumps A accommodated in the raw material accommodating cylindrical body 49 upward in order by the operation of a cylinder 52. In the supply of raw materials, as shown in FIG. 7 and FIG. 8, the arm 50 grips the raw material lump A projected from the raw material accommodating cylindrical body 49, moves forward by the operation of a cylinder 54, and throws the raw material lump A into the sleeve 27 from the position above the sleeve 27. After the arm 50 has returned to the original position, the cylinder 52 is actuated again to transfer the raw material lumps A accommodated in the raw material accommodating cylindrical body 49 upward by one step. After repetition of these steps and consumption of all raw material lumps A accommodated in one raw material accommodating cylindrical body 49 has been detected by a load sensor, the cylinder 52 is actuated to move the vertically reciprocating pin 51 downward so that it is pulled out of the hole portion 53. Thereafter, a stepping motor (not shown) rotates to turn round the turntable 48 only a predetermined angle so that the hole portion 53 of the next raw material accommodating cylindrical body 49 is located on the vertically reciprocating pin 51. In this way, the raw material lump A accommodated in the raw material accommodating cylindrical body 49 is supplied into the sleeve 27 one by one.

Next, the injection molding process using the apparatus mentioned above will be described. First, in such a state that a raw material lump A is placed in the raw material accommodating part formed by the inside wall of the sleeve 27 and the plunger 33, an electric current is passed through the high-frequency induction heating coil 37 and the raw material lump A is heated and melted. At this time, the movable upper mold 3 is clamped to the fixed lower mold 2, the vacuum extraction of the injection molding section space X in the vacuum housing 20 is performed, and the apparatus is ready for injection molding.

After the molten metal in the sleeve 27 has reached a predetermined temperature (measurement of the temperature may be performed by adopting any suitable method, such as a thermocouple disposed in the plunger 33 or a radiation pyrometer arranged in the fixed lower mold), the high-frequency induction heating coil 37 is demagnetized, the shutter cylinder 25 is actuated to open the shielding shutter 26, and the injection molding section space X communicates with the heating-melting section space Y. At this stage, the sleeve moving cylinder 32 and the injection cylinder 35 are immediately actuated synchronously, thus the sleeve 27 and the plunger 33 are elevated until the upper end of the sleeve 27 comes into close contact with the periphery of the pouring gate 4 of the mold 1, and at the same time the molten metal pressurized by the plunger 33 which is still elevated to a further predetermined distance is injected into and filled in the mold cavities 5, rapidly solidified because its heat is taken by the mold 1, and eventually molded. At this time, since the mold 1 is evacuated at the ejector section which is the terminal side of the flow of the molten metal through the mold exhaust vent 15 of the movable platen 11 and the flow of the molten metal follows the exhaust flow and is filled in the mold cavities 5, contamination of air bubbles cannot happen easily.

After the completion of injection molding, the sleeve 27 and the plunger 33 retreat to their original positions, the shielding shutter 26 is closed, then the movable platen 11 is elevated by the clamping cylinder 12, and the mold 1 is opened, as shown in FIG. 9. When the movable platen 11 reaches the top dead center, the upper end face of the connection rod 17 of the ejector pins 16 will assume the state of abutting against the lower end face of the cylinder rod 19 of the ejector cylinder 18. In this stage, since the solidified molded article B is separated from the fixed lower mold 2 together with the movable upper mold 3, the ejector cylinder 18 is actuated to protrude the ejector pin 16 downward, thereby separating the molded article B from the movable upper mold 3 and dropping it on the fixed lower mold 2. Subsequently, the molded article discharge cylinder 22 is actuated, and the arm section 23 moves forward, grasps the molded article B, and then retreats to take out the molded article B from the apparatus. After the discharge of the molded article, the clamping cylinder 12 is again actuated to close the mold 1, and the next injection cycle will be performed.

FIG. 10 shows a modification of the plunger. This plunger 33 a is different from the above-mentioned embodiment in that a collect chuck 55 is interposed between a cap-like upper head part 38 a and a hollow lower head part 38 b. This collect chuck 55 is caulked between the upper head part 38 a and the lower head part 38 b by pushing the upper head part 38 a into the collect chuck 55. Further, a metal plate 56 is interposed between the upper head part 38 a and the collect chuck 55 so that the upper head part 38 a may not contact a cooling medium fluid, such as water. Furthermore, two (which may be an arbitrary number) piston rings 46 are attached to the outer peripheral surface of the upper end portion of the lower head part 38 b so that their surfaces are flush with this outer peripheral surface. Incidentally, the hollow body part 39 is screwed into the lower head part 38 b, the hollow pipe part 40 is fixedly secured to the lower end of this body part 39, and the cooling medium supply pipe 43 is disposed in the internal spaces of the body part 39 and the hollow pipe part 40 so as to extend in the axial direction. Like the embodiment described hereinbefore, the cooling medium fluid, such as water and oil, supplied through the cooling medium supply pipe flows through the internal space of the plunger mentioned above from the leading end of the cooling medium supply pipe 43 along the circumferential wall and is discharged. As a material of the upper head part 38 a which is exposed to a high temperature, ceramics are preferred. As the other modification of attachment of the upper head part of the plunger, screwing, brazing, etc. may be considered.

The use of the injection mechanism described above has exhibited the effects shown in the following Table as compared with the case of the conventional sleeve and plunger which have not been cooled (a piston ring was also not used). Incidentally, in the case of the present invention the plunger having the structure shown in FIG. 10 was used. The cast alloy was an amorphous alloy (Zr₆₀Al₁₅Co_(2.5)Ni_(7.5)Cu₁₅ alloy). TABLE Without Cooling of Plunger Present and Sleeve, and also Invention without Piston Ring Penetration of  0 time/day 5 times/day Molten Metal (into a gap between plunger and sleeve) Operation Cycle 1-4 min./shot >90 min./shot Cleaning of penetrated part was required every time Number of times  0 time/day Shut-down and cleaning were of Shut-down required every injection

While preferred embodiments of the apparatus according to the present invention have been described hereinabove, the present invention is not limited to the above-mentioned embodiments and any changes in design may be adoptable. Although the apparatus of the present invention may be advantageously used in the injection molding of an active metal which tends to be oxidized and to be deteriorated by heating such as, for example, an alloy containing at least one active metal element selected among Al, Mg, Fe, Ti, Zr, Hf, Y, La, Ce, Nd, Sm and Mm (misch metal) in which the total of the active metal elements in the alloy is not less than 50 atomic %, it is not limited to this embodiment and may be used in the injection molding of various metals having a high melting point.

The apparatus of the present invention is particularly advantageously applicable to the injection molding of the amorphous alloy having a composition represented by either one of the following general formulas (1) to (6).

General formula (1): M¹ _(a)M² _(b)Ln_(c)M³ _(d)M⁴ _(e)M⁵ _(f)

wherein M¹ represents either or both of the two elements, Zr and Hf; M² represents at least one element selected from the group consisting of Ni, Cu, Fe, Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (misch metal: aggregate of rare earth elements); M³ represents at least one element selected from the group consisting of Be, B, C, N, and O; M⁴ represents at least one element selected from the group consisting of Ta, W, and Mo; M⁵ represents at least one element selected from the group consisting of Au, Pt, Pd, and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively satisfy 25 ≦a≦85, 15≦b≦75, 0≦c≦30, 0≦d≦30, 0≦e≦15, and 0≦f≦15.

General formula (2): Al_(100-g-h-i)Ln_(g)M⁶ _(h)M³ _(i)

wherein Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M⁶ represents at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M³ represents at least one element selected from the group consisting of Be, B, C, N, and O; and g, h, and i represent such atomic percentages as respectively satisfy 30 ≦g≦90, 0<h≦55, and 0≦i≦10.

General formula (3): Mg_(100-p)M⁷ _(p)

wherein M⁷ represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; and p represents an atomic percentage falling in the range of 5≦p≦60.

This amorphous alloy has large negative enthalpy of mixing and good producibility of the amorphous structure.

General formula (4): Mg_(100-q-r)M⁷ _(q)M⁸ _(r)

wherein M⁷ represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M⁸ represents at least one element selected from the group consisting of Al, Si, and Ca; and q and r represent such atomic percentages as respectively satisfy 1≦q≦35 and 1≦r≦25.

The filling of gaps in the amorphous structure of the alloy of the above general formula (3) with the M⁸ element having a small atomic radius (Al, Si, or Ca), as in this amorphous alloy, makes the structure stable and enhances the producibility of the amorphous structure.

General formula (5): Mg_(100-q-s)M⁷ _(q)M⁹ _(s)

General formula (6): Mg_(100-q-r-s)M⁷ _(q)M⁸ _(r)M⁹ _(s)

wherein M⁷ represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M⁸ represents at least one element selected from the group consisting of Al, Si, and Ca; M⁹ represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively satisfy 1≦q≦35, 1≦r≦25, and 3≦s≦25.

The addition of a rare earth element to the alloy of the general formula (3) or (4) mentioned above, as in these amorphous alloys, enhances the thermal stability of the amorphous structure.

Among other amorphous alloys mentioned above, the Zr-TM-Al and Hf-TM-Al (TM: transition metal) amorphous alloys having very wide differences between the glass transition temperature (Tg) and the crystallization temperature (Tx) exhibit high strength and high corrosion resistance, possess wide supercooled liquid ranges (glass transition ranges), ΔTx=Tx−Tg, of not less than 30 K, and extremely wide supercooled liquid ranges of not less than 60 K in the case of the Zr-TM-Al amorphous alloys. In the above temperature ranges, these amorphous alloys manifest very satisfactory workability owing to viscous flow even at such low stress not more than some tens MPa. They are characterized by being produced easily and very stably as evinced by the fact that they are enabled to furnish an amorphous bulk material even by a casting method using a cooling rate of the order of some tens K/s. Even by the mold casting from a melt and by the molding process utilizing the viscous flow resorting to the glass transition range as well, these alloys produce amorphous materials and permit very faithful reproduction of the shape and size of a mold cavity.

The Zr-TM-Al and Hf-TM-Al amorphous alloys to be used in the present invention possess very large range of Δ Tx, though variable with the composition of alloy and the method of determination. The Zr₆₀Al₁₅Co_(2.5)Ni_(7.5)Cu₁₅ alloy (Tg: 652 K, Tx: 768 K), for example, has such an extremely wide Δ Tx as 116 K. The Vickers hardness (Hv) of this alloy at temperatures from room temperature through the neighborhood of Tg is 460 (DPN), the tensile strength thereof is 1,600 MPa, and the bending strength thereof is up to 3,000 MPa. The thermal expansion coefficient, α of this alloy from room temperature through the neighborhood of Tg is as small as 1×10⁻⁵/K, the Young's modulus thereof is 91 GPa, and the elastic limit thereof in a compressed state exceeds 4-5%. Further, the toughness of the alloy is high such that the Charpy impact value falls in the range of 60-70 kJ/m^(2.) This alloy, while exhibiting such properties of very high strength as mentioned above, has the flow stress thereof lowered to the neighborhood of 10 MPa when it is heated up to the glass transition range thereof. This alloy, therefore, is characterized by being worked very easily and being manufactured with low stress into minute parts and high-precision parts complicated in shape. Moreover, owing to the properties of the so-called glass (amorphous) substance, this alloy is characterized by allowing manufacture of formed (deformed) articles with surfaces of extremely high smoothness and having substantially no possibility of forming a step which would arise when a slip band appeared on the surface as during the deformation of a crystalline alloy.

Generally, an amorphous alloy begins to crystallize when it is heated to the glass transition range thereof and retained therein for a long time. In contrast, the aforementioned alloys which possess such a wide Δ Tx range as mentioned above enjoy a stable amorphous phase and, when kept at a temperature properly selected in the ΔTx range, avoid producing any crystal for a duration up to about two hours. The user of these alloys, therefore, does not need to feel any anxiety about the occurrence of crystallization during the standard molding process.

The aforementioned alloys manifest these properties unreservedly during the course of transformation thereof from the molten state to the solidified state. Generally, the manufacture of an amorphous alloy requires rapid cooling. In contrast, the aforementioned alloys allow easy production of a bulk material of a single amorphous phase from a melt by the cooling which is effected at a rate of about 10 K/s. The solid bulk material consequently formed also has a very smooth surface. The alloys have transferability such that even a scratch of the order of microns inflicted by the polishing work on the surface of a mold is faithfully reproduced.

When the aforementioned alloys are adopted as a material for the ccasting, therefore, the mold to be used for producing the molded article is only required to have the surface thereof adjusted to fulfill the surface quality expected of the molded article because the molded product faithfully reproduces the surface quality of the mold, and therefore these alloys allow the steps for adjusting the size and the surface roughness of the molded article to be omitted or diminished.

The characteristics of the aforementioned amorphous alloys including in combination relatively low hardness, high tensile strength, high bending strength, relatively low Young's modulus, high elastic limit, high impact resistance, high wear resistance, smoothness of surface, and highly accurate castability render these alloys appropriate for use as the material for molded articles in various fields such as, for example, precision parts represented by ferrules, capillaries, sleeves or V-grooved substrates in optical connectors, toothed wheels, and micromachines. Since the amorphous alloy possesses highly accurate castability and machinability as well as excellent transferability capable of faithfully reproducing the contour of the cavity of the mold, the molded articles which satisfy dimensional prescription, dimensional accuracy, and surface quality can be manufactured by the mold casting method in a single process with high mass productivity insofar as the mold to be used is suitably prepared.

As a material to be used for the production of the amorphous alloy molded article to which the present invention is applied, any amorphous alloys heretofore known in the art such as, for example, amorphous alloys disclosed in JP 10-186176, JP 10-311923, JP 11-104281, and JP 11-189855 may be used besides the amorphous alloys mentioned above. The teachings of these patent literatures are incorporated here by references.

The injection molding apparatus of the present invention is suitable for the production of various molded articles of various metals, particularly active metals such as amorphous alloys.

While certain specific embodiments have been disclosed herein, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

The International Application PCT/JP2005/000377, filed Jan. 14, 2005, describes the invention described hereinabove and claimed in the claims appended hereinbelow, the disclosure of which is incorporated here by reference. 

1. An injection molding apparatus, comprising a mold having a pouring gate, a sleeve disposed so as to be movable forward and backward toward said pouring gate of said mold, a plunger slidably disposed in said sleeve, and a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of said sleeve and said plunger, wherein said plunger and/or said sleeve is equipped with a cooling means.
 2. The apparatus set forth in claim 1, wherein said plunger has an internal space formed therein and extending along its axial direction and a cooling medium supply pipe disposed in said internal space so as to leave a space portion around its leading end portion in the vicinity of a plunger head part and the circumference of a pipe wall, so that a cooling medium supplied through said cooling medium supply pipe may flow through the internal space of said plunger from its leading end.
 3. The apparatus set forth in claim 1, wherein said sleeve is provided at its outer peripheral surface with a cooling jacket having a flow path formed in the shape of bellows in its circumferential wall.
 4. The apparatus set forth in claim 3, wherein said cooling jacket is divided.
 5. The apparatus set forth in claim 1, wherein said plunger is formed from a metal or alloy having a melting point of not less than 800° C.
 6. The apparatus set forth in claim 1, wherein part or all of said plunger is formed from ceramic.
 7. The apparatus set forth in claim 1, wherein said plunger is provided with a piston ring disposed in the outer peripheral surface of a head part of said plunger.
 8. The apparatus set forth in claim 1, wherein said plunger has a main body part and a separate head part.
 9. The apparatus set forth in claim 1, wherein said sleeve is formed from ceramic.
 10. An injection molding apparatus, comprising a mold having a pouring gate, a sleeve disposed beneath said mold so as to be movable forward and backward toward said pouring gate of said mold, a plunger slidably disposed in said sleeve, a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of said sleeve and said plunger, and a raw material lump supplying means for supplying the raw material lump to said raw material accommodating part from above, wherein said plunger and/or said sleeve is provided with a cooling means.
 11. The apparatus set forth in claim 10, wherein said plunger has an internal space formed therein and extending along its axial direction and a cooling medium supply pipe disposed in said internal space so as to leave a space portion around its leading end portion in the vicinity of a plunger head part and the circumference of a pipe wall, so that a cooling medium supplied through said cooling medium supply pipe may flow through the internal space of said plunger from its leading end.
 12. The apparatus set forth in claim 10, wherein said sleeve is provided at its outer peripheral surface with a cooling jacket having a flow path formed in the shape of bellows in its circumferential wall.
 13. The apparatus set forth in claim 12, wherein said cooling jacket is divided.
 14. The apparatus set forth in claim 10, wherein said plunger is formed from a metal or alloy having a melting point of not less than 800° C.
 15. The apparatus set forth in claim 10, wherein part or all of said plunger is formed from ceramic.
 16. The apparatus set forth in claim 10, wherein said plunger is provided with a piston ring disposed in the outer peripheral surface of a head part of said plunger.
 17. The apparatus set forth in claim 10, wherein said plunger has a main body part and a separate head part.
 18. The apparatus set forth in claim 10, wherein said sleeve is formed from ceramic.
 19. The apparatus set forth in claim 10, wherein said raw material lump supplying means comprises an accommodating device containing a plurality of raw material lumps, a means for transferring the raw material lump disposed in said accommodating device to an upper position above said device, and a means for transferring the raw material lump transferred onto the upper position of the accommodating device to a position above the sleeve. 